Computers are important tools in today's society, and the computer display is an essential component of one's workspace. The importance of computer displays for the efficiency of work is demonstrated by the presence of larger displays and multiple displays when the display “real estate” becomes important to one's work. In some cases, larger displays allow for more “real estate” to be displayed. Dual displays are usually driven by independent display controllers, and the operating system (e.g. Windows 98™) is informed that the “desktop” or display surface is to be displayed on one side by one display controller and on the other side by the other display controller. This is typically done using two independent graphics subsystem accessing two separate and independent memory subsystems. Dual displays have an advantage over larger displays in many cases because with CRT monitors, the depth of the monitor is in proportion to the screen size, and large screens take up significant physical desktop surface area. It can sometimes be impossible to set up a 20″ CRT monitor, while it is possible to set up two 15″ monitors on the same desktop surface. The cost of two 15 inch monitors is also typically less than half that of one 20 inch monitor.
While providing a greater physical surface area for the computer display output provides satisfactory results in many work environments, there is a need to have better display detail for work requiring attention to detail, such as graphics work, in which a zoom or scaling of the area to be worked on is essential. Conventional zoom is done by the application programs themselves, i.e. the user selects a zoom level for a display, and the application provides a magnified view of the object being worked on, such as a document, drawing or image; mostly, this zoom covers or replaces the previous image on the display. Some application programs provide a smaller window with a representation of a whole page of a document or image, while the main viewing portion of the display provided the zoomed image.
Conventional zooming techniques operate to satisfaction when the applications provide them, however, the user often needs to command the application program to switch between zoom levels in order to edit a document correctly, since perspective is essential to proper editing. There is therefore a need to provide for a display-based zoom for providing a user with the ability to view an accurate zoom of a portion of a main display surface on one display, while being able to view the entire main display surface on the other in the case of multiple monitor configuration.
It is also known in the art to provide a single display controller hardware zoom in which the zoom operates to scale a fixed portion of a main surface memory, such as, for example, an area which is one quarter the size of the main surface memory, in which each pixel of the main surface memory is displayed as four pixels in the zoom display. The portion of the main surface memory can be displaced or dragged using the mouse. The known hardware zoom does not provide for a user defined magnification ratio to be used, and is limited to a fixed or a set of pre-defined magnification ratios,